The conventional ring rolling mill, widely used in practical applications, has a main roll that is driven to rotate at constant speed by electrical motor and reducer and to move in straight line by hydraulic cylinder or pneumatic pump, while the mandrel arbitrarily rotates. The ring blank experiences thickness decreasing and diameter enlarging, while the ring blank continuously goes through the gap between the main roll and mandrel. This mill and process have relative less parameter to adjust, even though the mill is low cost and easy to be manufactured.
For the conventional ring rolling mill, the mandrel can arbitrarily rotate and follow the ring blank because of the friction on their contact surfaces. The rotation speed of mandrel will change with different feeding and rotation speeds of main roll, and thus is arbitrarily and uncontrollable. This state of mandrel will causes the unstable state of the deformation zone of the ring blank, and the difference of the strain measure between the surface and inner of the rolled ring product will be 2-3 times or more. As a result, the rolled ring product will be low quality and short service life because of the uneven distribution strain, grains and hard phases, even though the rolled ring product meets the requirements of shape and dimensions. So it is very necessary to improve the ring rolling mill and process to get more stable plastic deformation method by enhancing the controlling of the ring rolling mill and process. This is the only way to obtain the finer grains and more homogeneous disperse phase for high quality ring products.